You will need one button. Sirdar used their button # B5611-0902.
You will also need stitch holders.

Finished measurements:
Chest circumference: 18.5(19.75, 21.25, 22, 22.75, 23.75)“ 47(50, 54, 56, 58, 60) cm
Finished length: 9.75(10.75, 11.75, 12.5, 13.5, 14)” 25(27, 30, 32, 34, 36)cm
Sleeve length: 6.25(6.5, 7, 8, 8.75, 9.75)“ 16(17, 18, 20, 22, 25) cm

Yarn used:
Sirdar Snuggly Cashmere Merino Silk DK
Shade 306 Slivery Moon (crew neck cardigan)
or
Shade 307 Pixie Dust (for Peter Pan collar cardigan)
3(4, 4, 5, 5, 5) balls

Booties - sized for 06(6-12, 12-24) months - 1 ball for all sizes